Method of manufacturing iwner tubes



May 15, 1923.

R. E. STEPHENSON METHOD OF MANUFACTURING INNER TUBES Filed Sept. 5, 1921Patented Ma 15, 1923.

UNl'l'ED STATES RALPHE. STEPHENSON, F INDIANAPOLIS, INDIANA, ASSIGNOR TOG. COMPANY, A CORPQEATION OF INDIANA.

86 T. TIRE METHOD OF MANUFACTURING INNER TUBES.

Application filed September 3, 1921. Serial No. 498,286.

To all whom it may concern:

Be it known that I, RALPH E. STEPHEN- SON. a citizen of the UnitedStates, residing at Indianapolis, county of Marion, and State ofIndiana, have invented a certain new and useful Method of ManufacturingInner Tubes, of which the following is a full, clear, and exactdescription.

This invention relates to an inner tubetor pneumatic tires and itsmethod oi manufacture.

It is desirable to incorporate what I is" .lmown as a valve base aroundthe opening in an inner. tube "for themetal valve stem by Which it isinflated. The valve base is usually made of one or more (usually 2 or"3) plies of super-posed fabric. Thetubes .of green stock are formedpreparatory to vulcaniz'ationin various Ways but most generally andeconomically by rolling'a sheet oi the proper dimensions around a pole asuitable number of times and the valve base, or patch asitmay becalled,'is generally ap,

plied to the front or first-coiled edge of the sheet in such wise as tolocate the base in direct contact with the pole? Frequently, air isentrapped at or in the vicinity of the patch in this method of procedureand causes blemishes in the finished tube, it being understood of coursethat the side of the tube that contacts with the poleis inverted andbecomes the outside of the finished vulcanized article. Still further,the fabricvalve base is usually apertured all or part way through,before being applied to the pole and covered by coils of greenstock, andduly ing the cure this pre-formed aperture is closed by "the flow of therubber, which is under more or less pressure by an envelopingcross-wrapper, consisting of a strip of fabric coiled splrally undermore or less tension about the green tube on the pole. This fill- I ingor" the hole, of course, rendered'it necessary to unch the tubeafter ithad been cured. unchingrequired a strip of Wood or soft metal tobeinserted in the tube to prevent the punch going through both of itswalls and necessitated an operation, adding to the cost of production.It the reinic'orc ing valve base is applied to the outside joi" thecoiled green tube, it is difficult, after curing, to locate the punch soas to make the hole in the exactcenter of the base, which is invisible,or substantially so. According the old methods or procedures therefor,Whether the patch is located so as to come to the inside or to theoutside of the finished tube, an operative could not quickly andreliably punch holes through the exact ,cen-

ter ofthe valve base. And still further, the

pressure otthe patch tends to flatten the stratum of rubber adjacent'theinserted anvil so that, after punching, the rubber stra tum contractsand becomes smaller in diameter than the hole through the fabric portionof the valve base. Consequently, a punch was used of a size making ahole in the fabriov reinforcement slightly larger than necessary. Andthis is obviously objectionable.

The present invention aims to produce a; new and improved tube in whichthe valve opening is molded therein during the. cure and preferably inthe centerof aifabr ic reinforcing valve base that is vulcanized in thewalls of the tube and substantially, it not completely, vconcealed fromview. The

invention also aims to permit molding thea valve opening in the tubeduring its manufacture in a practical and economic inanner, ,elnninat ngthe punching operation heretofore deemed necessary and theobjections,consequent punching.

applied thereto and with a hole-molding member in position, parts beingspaced and enlarged for the sake ofclearness.

Fig. 5 illustrates the cured and finished tubeona pole and in crosssection through the valve stem opening;.

Fig. 6 is a section similar to Fig. 5, to one .side of the valve stemopening;

Figs. 7 and 8 illustrate steps in a modified procedure.

, Usually in making inner tubes, a calendered sheet 1 of suitablevulcanizable rubber composition is laid on the tableand a pole Apreferred embodiment of the inventionis illustrated in the accompanyingdrawings in which 2 placed thereon parallel with one side and rolledover the sheet so as to ply it up into a tube, the latter beingindicated at 3.

The reinforcing valve base may be made in any suitable manner but, asshown in Fig. 3, is preferably made of a suitable number of plies ofwoven fabric l and vulcanizable rubber composition l of successivelyvaried size, these plies being super-posed upon one another in themanner illustrated. Then preferably, the valve base, indicated generallyby the numeral 5, is apertured centrally as indicated at 6. 1

According to the invention, and referring for the present to Figs. 1 to5, the preferred procedure is to apply the valve base 5 to the outsideof the formed tube 3 and with the largest ply of the base outermost asindicated in Fig. 4.

The next step in the preferred procedure is to insertahole-forming ormolding member Tin the aperture6 in the valve base, the

member 7 having preferably a sleeve or barrel portion 8 and a flange orabutment portion 9; i

Then the green tube is cross-wrapped, i. e., it iscompletely confined inover-lapping spiral convolutions of a strip of fabric applied under moreor less tension.

The tube thus prepared for curing is introduced in a steam heater, orotherwise treated, to completely vulcanize it. During the cure, therubber softens and the holeforming-member 7 is projected therethrough.Preferably, but not necessarily, the holeforming-member 7 1s providedwith a bevelled cutting" edge 8 for facilitating its movement throughthe stock.

After curing,the wrapper is removed and likewisealso the member '3'.Then the'cured tube is stripped from the pole, its ends splicedtogether, and a valve mounted in the opening that has been molded in thetube,

all in a manner well-known to those skilled in the art.

In the foregoing, the preferred method of procedure has been outlined.By locating the fabric valve base so that it is located on the inside,or at least nearer the in'sidethan the outside, of the finished tube,there is less likelihood of the product being blemished and thereinforcing or stiffening fabric 4 is disposed more advantageously. Bymold ing the hole for the valve stem, not only is the necessity ofpunching the tube avoided, but the walls in the opening 6 aresmootherand the cut edges ofthe'fabric better pro tected. It may be noted thatthe short plug of rubber that lies, or forms, within the'barrel 8 may bereadily removed on withdrawing the member 7. i I

The method of procedure may be varied in detail without departing fromthe prin ciples of the invention. lVhile not as desirable, the patch 5might be applied to the pole directly and covered over by coiling thetube stock thereabout as has been the practice. In such case, with alittle more time and care, the hole-forming-member 7 might be located inalignment with the hole 6 in the base and projected through the stockduring the cure by the action of the wrapper as before described. Butthis is obviously not as desirable as the preferred procedure described.Alternatively also, the patch might be incorporated between convolutionsof the green tube stock as illustrated in Fig. 7, and the hole-formingimember 7 positioned and projected through the layer of rubberover-lying-the'aperture in the valve base so as to imbed itselfin theunderlying convolutions of green stock; this case also, when the wrapperis plied under tension and the tubeis intro} duced into a heater, therewillbe substantially the same molding action asoccur"s in the preferredprocedure that has been de scribed in detail.

The form of the hole-forming-member may be varied. F or instance, asshown in Figs. 7 and 8, it may be a disk or plug 10. lfn this form,afterv plying up the green rubber sheet on the pole with thereinfor'cing valve base preferably but notnecess'a rily intermediate convolutionsthereof, the hole- :lorming-inember 10 may be pressed upon the outlyingthin layer or layers' of rubber covering the hole 6 and in sucha wayastto" carry the same against the underlying. can volutions of greenstock, as diagrammati cally illustrated in Fig. 7 The cured prod: not,before removal of the hole moldingmember 10, is illustrated in Fig. SIThthin layer, or film, of vulcanized rubber 11 underlying the -member 10(wh'i ch may be made very thin by increasing the thickness of the plug10) may be p'ressed out" in the' removal of the member 10, or cut or-brokeh as "desired (with the introduction ofth' valve stem, forinstance).

These and other changes in the details of the invention are contemplatedand refeii ence should, therefore, be made to theap a tubefromvulcanizable rubber composi tion, rolling a sheet of vulcani z ablerubber composition about a pole, making a laminated reinforcingvalve-base' of superposed plies of fabric successively varied insiie toform a skived margin, aperturing the reinforcing valve-base centrally,securing the reinforcing valve base to. the formed composition tubewith'itswidest ply outer? most, introducing a' flanged sleeve" intheopening in the reinforcing valve-base and holding it in place, curingthe tube thus formed, removing the flanged sleeve and splicing the endsof the tube.

2. A method of manufacturing inner tubes for pneumatic. tires whichconsists in sheathing a pole with vulcanizable rubber composition,applying a reinforcing Valvebase to the exterior of the compositiontube,

10 inserting a hole-forming-member in the tube through the center of thereinforcing valvebase, confining the tube and hole-formingmember,vulcanlzing the tube, removing the tube from the pole and turning itinside out, splicing the ends of the tube, and finally mounting a valvein the hole thus formed therein. 1 I

Signed at Indianapolis, this 31st day of August, 1921.

RALPH E. STEPHENSON.

